This application is based on applications Nos. 2000-81204 and 2001-44942 filed in Japan, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an optical disc device and, more specifically, to the device for setting the optimal recording power in the optical disc device that records information by emitting a laser beam to an optical disc recording medium.
2. Description of the Related Art
Optical disc devices of various types have been developed in recent years as a means for recording and reproducing large volumes of data, and various approaches have been taken to achieve ever higher recording densities. Phase change type optical disc devices that use the ability to effect a reversible change between crystalline and non-crystalline (amorphous) phases in the recording medium to record data are exemplary of one such approach.
A phase change type optical disc device records data by forming marks (amorphous parts) and spaces (crystalline parts) between the marks on the optical disc medium. The amorphous marks are formed by setting a semiconductor laser to a peak power level at which crystalline parts are changed to amorphous marks, and the crystalline spaces are formed by setting the semiconductor laser to a bias power level at which amorphous parts are converted to a crystalline state.
Reflectivity is different in marks and spaces. It is therefore possible to use this difference in reflectivity to read the recorded signal during data reproduction (reproduction).
The configuration of a conventional phase change type optical disc device is shown in FIG. 10. As shown in FIG. 10, the optical disk device comprises an optical head 1002, a reproduction section 1003, a reproduction signal quality detection section 1004, an optimal recording power determining section 1005, a recording section 1006, a laser drive circuit 1007, and a recording power setting section 1008.
FIG. 11 shows a track configuration of the optical disc 1001 in the prior art. This optical disc 1001 has recording areas in both a groove-shaped track (groove track 1101) and a track between the grooves (land track 1102). The groove track 1101 and land track 1102 form a continuous spiral by alternating with each other at each revolution of the disc.
When the optical disc 1001 is loaded into an optical disc device, the optical disc device performs trial recording to a predetermined area on the disc 1001, thereby determining an optimal laser power to be emitted for recording data to the disc 1001.
For that, when the optical disc 1001 is loaded into an optical disc device, specific operations are first performed to detect the disc type and information for controlling disc rotation. The optical head 1002 then moves to an area reserved for setting the optimal recording power.
Both the peak power level and bias power level must be determined in a phase change type optical disc device. Determining the peak power level is explained below.
The recording power setting section 1008 first sets initial peak power and bias power levels for the laser drive circuit 1007. The power level set for recording to land tracks and the power level set for recording to groove tracks are equal at this time.
The recording section 1006 then sends a signal for continuously recording a land track for one revolution and a groove track for one revolution from a specified starting point to the laser drive circuit 1007 for recording by the optical head 1002. The output beam from the semiconductor laser that is a component of the optical head 1002 is focused on the optical disc 1001 as a spot to form a mark. The shape of the mark is determined by the waveform of the emitted laser beam.
When recording the land and groove tracks is completed, the semiconductor laser of the optical head 1002 is driven at the reproduction power level to reproduce the signal previously recorded to the land and groove tracks. The reproduction signal 1009, which varies according to the presence or absence of a recording mark on the optical disc 1001, is input to the reproduction section 1003. The reproduction section 1003 then amplifies, waveform-equalizes, and digitizes the reproduction signal 1009, and passes the resulting signal 1010 to the reproduction signal quality detection section 1004.
The reproduction signal quality detection section 1004 detects the signal quality of signal 1010, and inputs the result to optimal recording power determining section 1005.
It should be noted that the reproduction signal quality detection section 1004 detects BER (Byte Error Rate) of the recorded signal when it is reproduced. The BER detected here is the average over the reproduced track. FIG. 12 shows the relationship between peak power and BER.
Peak power is shown on the axis of abscissas and BER on the axis of ordinates in FIG. 12. In general, a lower BER indicates that recording is more accurate, under the same reproduction conditions. An xe2x80x9cOKxe2x80x9d (good) detection result is therefore output if the BER is less than a specific threshold value, and a xe2x80x9cNGxe2x80x9d (no good) detection result is output if the BER is greater than or equal to the threshold value.
The optimal recording power determining section 1005 determines the recording power (peek power), for example, according to a procedure indicated by a flowchart shown in FIG. 13.
The optical head moves to a predetermined area provided for setting a laser power emitted onto the optical disc 1001 (S101) and an initial value of the recording power is set (S102). Subsequently, data are recorded onto the power setting area on the disc 1001 with the set recording power and then the recorded data are reproduced (S103). The quality of the reproduced signal is detected by detecting BER from the reproduced signal (S104). Based on the current detection result and the previous detection result, two peak powers are determined with which the quality of the reproduced signal changes xe2x80x9cOKxe2x80x9d to xe2x80x9cNGxe2x80x9d or xe2x80x9cNGxe2x80x9d to xe2x80x9cOKxe2x80x9d (S104 to S108). After determining those two powers, the optimal power is determined by averaging values of those powers (S109) and adding a predetermined margin to the averaged value (S110).
For example, when the first detection result from the reproduction signal quality detection section 1004 is xe2x80x9cNGxe2x80x9d the peak power level is set higher than the initial peak power (S108). When the result is xe2x80x9cOKxe2x80x9d, the peak power level is set below the initial peak power (S106). The reset peak power level is then used to record and reproduce the land track and groove track again, and repeat the above evaluation.
Then, when the first detection result from the reproduction signal quality detection section 1004 is xe2x80x9cNGxe2x80x9d (S104) and the second result is xe2x80x9cOKxe2x80x9d (S107), the optimal recording power determining section 1005 takes the average of the previous peak power setting and the subsequent or current peak power setting, adds a predetermined margin, and uses the result as the optimal recording power (S109, S110).
When the first detection result from the reproduction signal quality detection section 1004 is xe2x80x9cOKxe2x80x9d (S104) and the second result is xe2x80x9cNGxe2x80x9d (S105), the optimal recording power determining section 1005 takes the average of the previous and current peak power settings, adds a predetermined margin, and uses the result as the optimal recording power (S109, S110).
With the conventional method as described above, the detected BER is the average for the reproduced track. Therefore, reproduction errors increase if there are fingerprints, for example, on the track used for BER detection, causing the BER to be higher than expected. As a result, this causes a power level greater than the actual optimal peak power level to be set as the optimal recording power level.
The present invention is directed to a solution for the aforementioned problem by providing an optical disc device and a recording power determining method used in the disc device for determining the optimal recording power even when fingerprints are on the track used for the trial recording operation which determines the emission power for recording.
In a first aspect of the invention, a method is provided of determining a recording power which is a laser emission power used for data recording in an optical disc device for recording data to an optical disc. The optical disc having a plurality of tracks each connecting to form a continuous spiral, each track comprising a plurality of sectors. The method comprises setting a plurality of recording power settings, recording specific data to predetermined sectors in predetermined areas with a recording power at each of the set recording power settings, and reproducing the recorded data from each sector to detect, for each sector, a quality of a reproduction signal which is generated by reproducing the recorded data, and determining an amount of the recording power to be used for data recording based on the detection result of the quality of the reproduction signal which is obtained for each sector and for each recording power setting.
The method may further comprise, based on the detection result of the quality of the reproduction signal, obtaining at least one of the plurality of recording power settings with which the number of sectors each having quality of the reproduction signal to meet a predetermined condition are more than or equal to a predetermined number, and determining the amount of the recording power based on the obtained at least one of the recording power settings.
The method may further comprise obtaining a first power setting with which the number of sectors each having quality of the reproduction signal to meet a predetermined condition are more than or equal to the predetermined number and a second power setting with which the number of sectors each having quality of the reproduction signal to meet a predetermined condition are less than the predetermined number, and determining the amount of the recording power based on the first and second recording power settings.
In the method, error rate or jitter of the reproduction signal may be detected as the quality of the reproduction signal.
In the method, a detection result to a sector of which the quality of reproduction meets a predetermined condition which defines a defect of the sector may not be included in the detection results used for determining the amount of the recording power.
In the method, wherein in recording the specific data, data as the specific data which are different from data which has been recorded in a previous time are recorded to each sector.
In the method, the specific data to be recorded may be recorded to each sector after deleting the recorded specific data.
In a second aspect of the invention, an optical disc device is provided for recording data to an optical disc. The optical disc have a plurality of tracks each connecting to form a continuous spiral. Each track comprising a plurality of sectors. The device comprises a setting section for setting a plurality of recording power settings, the recording power being a laser emission power used for data recording, a recording section for recording specific data to predetermined sectors in predetermined areas with a recording power at each of the set recording power settings, and a reproducing section for reproducing the recorded data from each sector to detect, for each sector, a quality of a reproduction signal which is generated by reproducing the recorded data, and a determining section for determining an amount of the recording power to be used for data recording based on the detection result of the quality of the reproduction signal which is obtained for each sector and for each recording power setting.